Single-stage process for preparing glycol monoethers from olefins

ABSTRACT

A process for preparing glycol monoethers from olefins comprises reacting the olefins with an epoxidizing reagent in the simultaneous presence of hydroxyl-containing organic compounds over a mixture of epoxidation catalysts and alkoxylation catalysts.

[0001] The present invention relates to an improved process forpreparing glycol monoethers from olefins. The invention further relatesto a catalyst mixture which is used in the process of the presentinvention.

[0002] Glycol monoethers are widely used industrially as solvents,absorption liquids in gas scrubbing, antifreezes, hydraulic fluids,lubricants, plasticizers, surfactants, precursors for fiber productssuch as polyesters or urethanes, additives for printing inks and incosmetic and skincare products.

[0003] The most important products are the corresponding glycol ethersof ethylene and propene. These glycol ethers are usually prepared byreacting epoxides of the parent olefins with the corresponding alcohols.

[0004] A disadvantage of this procedure is that a multi-stage process isrequired which involves initial preparation of the epoxides from theolefins followed by ring-opening reaction of the epoxides with alcoholsat a higher temperature using, for example, sulfuric acid.

[0005] It is an object of the present invention to provide a simplerprocess for preparing glycol monoethers.

[0006] We have found that, surprisingly, this object is achieved and theabove-described disadvantages are overcome by a simple single-stage-synthesis which involves reacting olefins with a conventionalepoxidizing reagent over suitable epoxidation catalyts andsimultaneously allowing the presence of hydroxyl-containing organiccompounds, such as alcohols, and acidic or basic alkoxylation catalysts.The epoxide intermediates are reacted in situ over the addedalkoxylation catalysts to give glycol monoethers.

[0007] The present invention accordingly provides a process forpreparing glycol monoethers from olefins, which comprises reacting theolefins with an epoxidizing reagent in the simultaneous presence ofhydroxyl-containing organic compounds over a mixture of epoxidationcatalysts and alkoxylation catalysts.

[0008] Preferred epoxidation catalysts in the catalyst mixture aretitanium-containing silicates or titanium-, vanadium-, germanium- ortin-containing zeolites, in particualr titanium or vanadium silicaliteshaving a zeolite structure assigned by X-ray diffraction to the MFI,MEL, BEA, MTW, TON, FER or MFI/MEL mixed structure. Such epoxidationcatalysts are described, for example, in DE-A 44 25 672. According toDE-A 44 25 672, the abovementioned titanium or vanadium silicalites maycontain noble metals such as platinum metals in amounts of 0.01-20% byweight,. which is particularly advantageous when the epoxidizing reagentused is a hydrogen/oxygen mixture.

[0009] Preferred alkoxylation catalysts in the catalyst.mixture areacidic catalysts in the form of mineral acids or in the form of solidacidic heterogeneous catalysts, and solid basic catalysts.

[0010] Examples of mineral acids are sulfuric acid, hydrochloric acidand orthophosphoric acid; for the purposes of the present invention,mineral acids include sufficiently acidic organic sulfonic acids andcarboxylic acids such as p-toluenesulfonic. acid, methanesulfonic acidor trifluoroacetic acid.

[0011] Solid alkoxylation catalysts are particularly suitable, i.e.those which do not dissolve in the reaction medium and which are presentas solid phase (as heterogeneous catalysts) during the reaction.

[0012] Preference is given to solid acidic heterogeneous catalysts basedon supported mineral acids, polymeric acidic ion exchange resins,composites of acidic ion exchange resins in inorganic materials, acidicmetal oxides or acid zeolites. Examples of such heterogeneous catalystsare K10-type acidic sheet silicates, acidic metal oxides as described byArata in Appl. Catalysis A: General 146 (1996), 3-32, and acidiczeolites of the structure type MFI (for example B-ZSM-5 zeolite), MEL,MFI/MEL, BEA (for example H-B-β-zeolite), MOR, FER, NES, ERI, OFF, MAZ,FAU, TON, CRA, RUT, BOG, LTA, NON, MTN, HEU, AFI, MTW, DOE, EUO, MTT,RHO, CAN, LTL, GIS, GME, VFI, EMT, DDR, SGT, CON, ZON or MFS.

[0013] Preference is furthermore given to solid basic catalysts based onalkali metal or alkaline earth metal oxides or hydroxides, supportedbases, polymeric basic ion exchange resins, dendrimeric amines, talcitesor hydrotalcites.

[0014] The above-described catalyst mixture usually comprises from 1 to99 parts by weight of epoxidation catalysts and from 99 to 1 parts byweight of alkoxylation catalyts, when the latter are present in solidform, i.e. as heterogeneous catalysts. Preferred ranges for theproportions of these two types of catalyst are 5-95 parts by weight/95-5parts by weight and in particular 20-80 parts by weight: 80-20 parts byweight. The above-described catalyst mixture may additionally comprisefurther conventional auxiliaries. When free mineral acids are present asalkoxylation catalysts, the proportion of epoxidation catalysts toalkoxylation catalysts is usually 90-99.999 parts by weight: 10-0.001parts by weight, in particular 99-99.99 parts by weight: 1-0.01 parts byweight.

[0015] Since the above-described mixture of the solid epoxidationcatalysts and the solid alkoxylation catalysts is novel, the presentinvention also provides a catalyst mixture for the single-stageepoxidation and alkoxylation of olefins, consisting of from 1 to 99parts by weight of epoxidation catalysts and from 99 to 1 part by weightof solid alkoxylation catalysts.

[0016] Particularly useful epoxidizing reagents for the process of thepresent invention are aqueous hydrogen peroxide or a hydrogen/oxygenmixture. The use of hydrogen/oxygen mixtures for epoxidation isdescribed, for example, in DE-A 44 25 672. However, organic peracids orhydroperoxides are also useful as epoxidizing reagents.

[0017] Hydroxyl-containing organic compounds are in principle any mono-and polyhydroxy compounds having sufficient O—H acidity. Preference isgiven to linear or branched C₁- to C₂₀-alkanols, C₅- to C₈-cycloalkanolsand C₇- to C₂₀-arylalkanols. Examples of such alcohols are methanol,ethanol, propanol, isopropanol, butanol, isobutanol, sec-butanol,tert-butanol, pentanol, isopentanol, sec-pentanol, tert-pentanol,neopentanol, hexanol, heptanol, octanol, 2-ethylhexanol, nonanol,isononanol, decanol, undecanol, dodecanol, tridecanol, isotridecanol,tetradecanol, pentadecanol, hexadecanol, heptadecanol, octadecanol,eicosanol, cyclopentanol, cyclohexanol, cycloheptanol, cyclooctanol,benzyl alcohol, 2-phenylethanol, 3-phenylpropanol and 4-phenylbutanol.It is also possible to use mixtures of the abovementioned alcohols. Veryparticular preference is given to C₁- to C₈-alkanols.

[0018] The hydroxyl-containing organic compounds are used instoichiometric amounts or in excess, based on the ethylenicallyunsaturated double bond equivalents of the olefin, and also as solvent.If the hydroxyl-containing compounds also react with additionalfunctional groups in the olefins, the amount of hydroxyl-containingcompounds has to be increased accordingly.

[0019] The olefin used can be any organic compound which contains atleast one ethylenically unsaturated double bond. It may be aliphatic,aromatic or cycloaliphatic and may consist of a linear or branchedstructure. The olefin is preferably of from 2 to 30 carbon atoms. Morethan one ethylenically unsaturated double bond may be present, forexample in dienes or trienes. The olefin may additionally containfunctional groups, such as halogen atoms, carboxyl groups, carboxylicester functions, hydroxyl groups, ether bridges, sulfide bridges,carbonyl functions, cyano groups, nitro groups or amino groups.

[0020] Typical examples of such olefins are ethylene, propene, 1-butene,cis- and trans-2-butene, 1,3-butadiene, pentenes, isoprene, hexenes,octenes, nonenes, decenes, undecenes, dodecenes, cyclopentene,cyclohexene, dicyclopentadiene, methylenecyclopropane, vinylcyclohexane,vinylcyclohexene, allyl chloride, acrylic acid, methacrylic acid,crotonic acid, vinylacetic acid, allyl alcohol, alkyl acrylates, alkylmethacrylates, oleic acid, linoleic acid, linolenic acid, esters andglycerides of such unsaturated fatty acids, styrene, α-methylstyrene,divinylbenzene, indene and stilbene. Mixtures of the stated olefins mayalso be used in the process of the present invention.

[0021] The process of the present invention is particularly suitable forpreparing glycol monoethers from linear or branched C₂- to C₅-alkenes,in particular propene.

[0022] The glycol monoethers produced by the process of the presentinvention contain the structural units

[0023] where R is the residue of the hydroxyl-containing organiccompound used. The glycol monoethers are frequently isomeric mixtures inwhich the OH group and the OR group are interchanged.

[0024] The reaction conditions for the process of the present inventionwith respect to temperature, pressure, mode of addition of the startingmaterials and the reaction time vary depending on the structures of thestarting materials. As a rule, the reactivity of the system decreaseswith increasing chain length or increasing molecule size of olefins usedand hydroxyl-containing organic compounds used, thus necessitating moresevere reaction conditions.

[0025] Typical reaction conditions for the reaction of linear orbranched C₂- to C₅-alkenes, which are mostly gaseous under standardconditions, with aqueous H₂O₂ in the presence of C₁- to C₈-alkanols,which are usually present in excess, are as follows: temperature from−30° C. to +80° C., in particular from −10° C. to +50° C., underautogeneous pressure at reaction temperature, reaction time from 1 to 10hours.

[0026] The process of the present invention can be carried out on alaboratory scale and on an industrial scale, in batchwise or continuousoperation. The reactants can be contacted with the catalyst mixture inboth a slurry and a fixed bed procedure. The reaction may be carried outin the gas phase, liquid phase or supercritical phase, preference beinggiven to the liquid phase.

[0027] A further advantage is that the use of heterogeneous epoxidationand alkoxylation catalysts allows regeneration of deactivated catalystsby washing with the alcohol to be used in the reaction or thermallyunder oxidizing conditions.

[0028] In many cases, the process of the present invention provides forvirtually complete conversion of the olefins to the glycol monoethers.If substantial amounts of epoxide intermediates are still present in thefinal product, these can usually be completely removed by simplemethods, for example by distillation or gas expulsion (in the case ofvolatile epoxides such as propylene oxide).

[0029] The examples which follow illustrate the invention withoutrestricting it. The preparation conditions, conversions and yields werenot optimized.

EXAMPLES Example 1

[0030] Preparation of an Epoxidation Catalyst

[0031] 455 g of tetraethyl orthosilicate were placed in a 2 1four-necked flask and 15 g of tetraisopropyl orthotitanate were added inthe course of 30 minutes from a dropping funnel while stirring (250 rpm,paddle stirrer). A colorless, clear mixture formed. Finally, 800 g of a20% strength by weight tetrapropylammonium hydroxide solution (alkalimetal content <10 ppm) were added and stirring was continued for afurther hour. The alcohol mixture (about 450 g) formed by hydrolysis wasdistilled off at from 90° C. to 100° C. After addition of 1.5 1 ofdeionized water, the now slightly opaque sol was transferred to astirred 2.5 1 stainless steel autoclave.

[0032] The closed autoclave (anchor stirrer, 200 rpm) was brought to areaction temperature of 175° C. at a heating rate of 3° C./min. Thereaction was stopped after 92 hours. The cooled reaction mixture (whitesuspension) was centrifuged and the resulting solid was washed neutralseveral times with water. The solid obtained was dried at 110° C. in thecourse of 24 hours (weight obtained 149 g). Finally, the template stillpresent in the zeolite was burnt off in air at 550° C. in the course of5 hours (loss on calcination: 141 by weight).

[0033] The pure white product had a titanium content of 1.5% by weightand a residual alkali metal content of less than 100 ppm, according towet chemical analysis. The yield based on SiO₂ used was 97%. Thecrystallite size was about 0.05-0.25 μm and the product showed a typicalinfrared band at about 960 cm⁻¹.

Example 2

[0034] Preparation of an Alkoxylation Catalyst

[0035] 60.0 g of boric acid were dissolved in a solution of 343.8 g oftetraethylammonium hydroxide (40% by weight in water) and 206.2 g ofdeionized water in a beaker. This solution was transferred into astirred 2.5 1 stainless steel autoclave. 550.0 g of colloidal silica sol(Ludox® AS40) were added to this mixture with stirring.

[0036] The mixture was crystallized at 150° C. over the course of 216hours, separated off, washed with deionized water and dried at 120° C.for 24 hours. The weight obtained was 279 g. Finally, the product wascalcined at 500° C. in air over the course of 5 hours t give theH-B-β-zeolite.

Example 3

[0037] Single-Stage Preparation of a Glycol Monoether from Propene andMethanol

[0038] 45 ml of methanol, 1.5 g of titanium silicalite powder fromExample 1 and 1.5 g of zeolite B-ZSM-5 were placed in a 250 ml glassautoclave and the suspension was stirred using a magnetic stirrer. Theclosed glass autoclave was then cooled to −30° C. and pressurized with20.7 g of propene. The glass autoclave was then warmed to 0° C. and 30 gof a 30% strength by weight hydrogen peroxide solution were metered in.The reaction mixture was stirred at 0° C. under autogeneous pressure for5 h. The catalyst was then removed by centrifugation and the solutionwas analyzed by gas chromatography. The solution contained 9.7% byweight of propylene oxide and 8.2% by weight of methoxypropanols.

Example 4

[0039] Single-Stage Preparation of a Glycol Monoether from Propene andEthanol

[0040] 45 ml of ethanol, 1.5 g of titanium silicalite powder fromExample 1 and 1.5 g of zeolite H-ZSM-5 were placed in a 250 ml glassautoclave and the suspension was stirred using a magnetic stirrer. Theclosed glass autoclave was then cooled to −30° C. and pressurized with20.7 g of propene. The glass autoclave was then warmed to 0° C. and 30 gof a 30% strength by weight hydrogen peroxide solution were metered in.The reaction mixture was stirred at 0° C. under autogeneous pressure for5 h. The catalyst was then removed by centrifugation and the solutionwas analyzed by gas chromatography. The solution contained 4.5% byweight of propylene oxide and 2.2% by weight of ethoxypropanols.

Example 5

[0041] Single-Stage Preparation of a Glycol Monoether from Propene andButanol

[0042] 45 ml of butanol, 1.5 ml of titanium silicalite powder fromExample 1 and 1.5 g of H-B-β-zeolite were placed in a 250 ml glassautoclave and the suspension was stirred using a magnetic stirrer. Theclosed glass autoclave was then cooled to −30° C. and pressurized with20.7 g of propene. The glass autoclave was then warmed to 0° C. and 30 gof a 30% strength by weight hydrogen peroxide solution were metered in.The reaction mixture was stirred at 0° C. under autogeneous pressure for5 h. The catalyst was then removed by centrifugation and the solutionwas analyzed by gas chromatography. The solution contained 0.3% byweight of propylene oxide and 3.8% by weight of butoxypropanols.

Example 6

[0043] Single-Stage Preparation of a Glycol Monoether from Propene andEthanol

[0044] 45 ml of ethanol, 1.5 ml of titanium silicalite powder fromExample 1 and 1.5 g of polymeric, acidic cation exchanger (Lewatit@,from Bayer) were placed in a 250 ml glass autoclave and the suspensionwas stirred using a magnetic stirrer. The closed glass autoclave wasthen cooled to −30° C. and pressurized with 20.7 g of propene. The glassautoclave was then warmed to 0° C. and 30 g of a 30% strength by weighthydrogen peroxide solution were metered in. The reaction mixture wasstirred at 0° C. under autogeneous pressure for 5 h. The catalyst wasthen removed by centrifugation and the solution was analyzed by gaschromatography. The solution contained 4.5% by weight of propylene oxideand 2.2% by weight of ethoxypropanols.

Comparative Example A

[0045] Single-Stage Preparation of a Glycol Monoether from Propene andMethanol

[0046] 45 ml of methanol and 1.5 g of titanium silicalite powder fromExample 1 were placed in a 250 ml glass autoclave and the suspension wasstirred using a magnetic stirrer. The closed glass autoclave was thencooled to −30° C. and pressurized with 5.8 g of propene. The glassautoclave was then warmed to 0° C. and 32 g of a 30% strength by weighthydrogen peroxide solution were metered in. The reaction mixture wasstirred at 0° C. under autogeneous pressure for 2 h. The catalyst wasthen removed by centrifugation and the solution was analyzed by gaschromatography. The solution contained 8.65% by weight of propyleneoxide, 0.04% by weight of methoxy-2-propanol and 0.09% by weight ofmethoxy-3-propanol.

We claim:
 1. A process for preparing glycol monoethers from olefins,which comprises reacting the olefins with an epoxidizing reagent in thesimultaneous presence of hydroxyl-containing organic compounds over amixture of epoxidation catalysts and alkoxylation catalysts.
 2. Aprocess as claimed in claim 1 , wherein the epoxidation catalysts usedin the catalyst mixture are titanium-containing silicates or titanium-,vanadium-, germanium- or tin-containing zeolites, in particular titaniumor vanadium silicalites having a zeolite structure assigned by X-raydiffraction to the MFI, MEL, BEA, MTW, TON, FER or MFI/MEL mixedstructure.
 3. A process as claimed in claim 1 or 2 , wherein thealkoxylation catalysts used in the catalyst mixture are acidic catalystsin the form of mineral acids or in the form of solid acidicheterogeneous catalysts, or solid basic catalysts.
 4. A process asclaimed in claim 3 , wherein the acidic alkoxylation catalysts used inthe catalyst mixture are solid heterogeneous catalysts based onsupported mineral acids, polymeric acidic ion exchange resins,composites of acidic ion exchange resins in inorganic materials, acidicmetal oxides or acidic zeolites.
 5. A process as claimed in claim 3 ,wherein the basic alkoxylation catalysts used in the catalyst mixtureare solid basic catalysts based on alkali metal or alkaline earth metaloxides or hydroxides, supported bases, polymeric basic ion exchangeresins, dendrimeric amines, talcites or hydrotalcites.
 6. A process asclaimed in any of claims 1 to 5 , wherein the epoxidizing reagent usedis aqueous hydrogen peroxide or a hydrogen/oxygen mixture.
 7. A processas claimed in any of claims 1 to 6 , wherein the hydroxyl-containingorganic compounds used are linear or branched C₁- to C₂₀-alkanols, C₅-to C₈-cycloalkanols or C₇- to C₂₀-arylalkanols.
 8. A process as claimedin any of claims 1 to 7 , wherein the olefins used are those having from2 to 30 carbon atoms and one or more ethylenically unsaturated doublebonds.
 9. A process as claimed in claim 8 , wherein the olefins used arelinear or branched C₂- to C₅-alkenes, in particular propene.
 10. Acatalyst mixture for the single-stage epoxidation and alkoxylation ofolefins, consisting of from 1 to 99 parts by weight of epoxidationcatalysts and from 99 to 1 parts by weight of solid alkoxylationcatalyts.